Experimental Design Details
ALLOCATION TO TREATMENTS:
The 1,329 participants were divided into three groups of equal size. The three groups are balanced in terms of the recruitment process.
INTERVENTION:
We let the sample rest until February 9th, 2024.
The intervention consists of sending one text message to each participant. In each group half of the participants will receive the message on February 10th 2024, while the other half will receive the message on February 24th 2024. In between the two sending dates, the group that receives the message later (on February 24th) will be used to quantify the effect of receiving a message.
All the participants receive the following message, and this is the only message that the control group receives:
"Thanks for participating in this study on bio-waste recycling conducted by Universitat de les Iles Balears. Did you know that each week that a citizen of Palma recycles their bio-waste, they reduce, approximately, CO2 emissions by the same amount as a tree absorbs in 17 days?"
Note: in the statement "Did you know that each week that a citizen of Palma recycles their bio-waste, they reduce, approximately, CO2 emissions by the same amount as a tree absorbs in 17 days?", the number 17 was calculated based on past bio-waste sorting data provided to us by the waste management company Emaya combined with the CO2 emission equivalences provided by Fan et al. (2020a,b) and the European Environment Agency (2016)
The participants in the "incentives treatment" also receive the following text:
"Recycling has a prize this fortnight! For each week that someone in your household uses a bio-waste recycling bin between 02/12/2024 [02/26/2024] and 02/25/2024 [03/10/2024] (both inclusive), you will obtain one chance to win one out of five prizes of 280 euros"
The participants in the "Kantian treatment" also receive the following text:
"Imagine by how much CO2 emissions would be reduced if your household recycled its biowaste and all the other households in Palma also did the same as yours!"
All the participants receive a closing message with a link providing information about the study. The platform used for sending the messages can track the participants who clicked the link.
TIME HORIZON OF THE STUDY:
To evaluate the effects of the intervention in the medium-long term, we will wait for a minimum of 3 months to start running the analysis.
OTHER INFO/COMMENTS:
1. The last week of February and the first of March 2023, we conducted a lab-experiment designed to test the effects of several messages. This lab-experiment was used to tailor the field intervention.
2. If feasible, after the intervention (in June or July 2024), we will run a post-intervention survey to collect information about the mechanisms at work.
REFERENCES:
Van Fan, Y., Nevrlýb, V., Šompláka, R., & Smejkalováb, V. (2020). The Potential of Carbon Emission Footprint Reduction from Biowaste in Mixed Municipal Solid Waste: EU-27. Chemical Engineering, 81.
Van Fan, Y., Klemeš, J. J., Walmsley, T. G., & Bertók, B. (2020). Implementing Circular Economy in municipal solid waste treatment system using P-graph. Science of The Total Environment, 701, 134652.
European Environment Agency (2016) EEA Report No 5/2016 (2016). European forest
ecosystems. State and trends. Luxembourg.